Apparatus for ejecting a mixture of liquids

ABSTRACT

Two mutually reactive liquids, such as the components of a polyurethane foam, are mixed together and ejected onto a substrate by means of apparatus that pumps the liquids separately and remotely mixes them only at the last moment. Heretofore, the liquids were separately pumped by means of parallel reciprocating proportioning pumps to which the liquids are fed under pressure; and as a result of this feed pressure the outlet pressure of the pumps varied with respect to the direction of stroke. By rearranging the pumps in tandem opposed relation, and driving them by a constant pressure motor such as a double-acting fluid motor, a counterbalancing effect is created which effectively reduces the pressure variation as the stroking action reverses.

United States Patent Gusmer et al.

[ Oct. 16, 1973 [76] Inventors: Frederick E. Gusmer, Mantoloking;

Carl W.'Sundberg, Jr., Chatham; Joseph E. Hayes, Jr., Manasquan, all ofNJ.

[22] Filed: Nov. 30, 1972 [21] Appl. No.: 310,947

[52] US. Cl 239/61, 239/332, 239/413, 137/566 [51] Int. Cl B05b 7/04,B05b 9/04, B05b 7/12 [58] Field of Search 239/61, 93, 94, 321, 239/322,331, 332, 407, 413; 137/566, 567

[56] References Cited UNITED STATES PATENTS 2,548,987 4/1951 Mayo137/566X 2,819,928 l/1958 Liedberg 239/322 X 3,128,782 4/1964 Limpert eta1. 137/566 X 3,193,202 7/1965 Liggenstorfer et a1. 239/332 X 3,286,93311/1966 Savage; 239/332 X 8/1967 Schoenecker et a1. 239 332X 8/1967Tibbitt ..239/331x Primary Examiner-Robert S. Ward, Jr. Att0rneylrvin S.Thompson [5 7] ABSTRACT Two mutually reactive liquids, such as thecomponents of a polyurethane foam, are mixed together and ejected onto asubstrate by means of apparatus that pumps the liquids separately andremotely mixes them only at the last moment. I-leretofore, the liquidswere separately pumped by means of parallel reciprocating proportioningpumps to which the liquids are fed under pressure; and as a result ofthis feed pressure the outlet pressure of the pumps varied with respectto the direction of stroke. By rearranging the pumps in tandem opposedrelation, and driving them by a constant pressure motor such as adouble-acting fluid mo-' tor, a counterbalancing effect is created whicheffectively reduces the pressure variation as the stroking actionreverses.

5 Claims, 1 Drawing Figure ACTIVATOR l5 SUMP RESIN APPARATUS FOREJECTING A MIXTURE OF LIQUIDS The present invention relates to apparatusfor ejecting a mixture of liquids, more particularly a mixture ofmutually reactive liquids such as those that form a foam on a substrateand that cure by reacting with each other, for example, the componentsof a polyurethane foam and elastomeric coatings.

Such mixtures of liquids are ejected from a mixing chamber underpressure onto a substrate, for example by apparatus such as is disclosedin Gusmer US. Pat. Nos. 2,890,836 and 3,263,928. As the liquids arehighly reactive with each other, they cannot be mixed together in theapparatus until the last possible moment, or else they will react in theapparatus and clog the apparatus. Therefore, as the mixture must beejected under pressure, it is necessary to pump the mutually reactiveliquids to elevated pressure by separate pump means, the reactiveliquids following generally parallel flow paths from separate sources ofthe respective liquids to the mixing chamber from which they are ejectedonto the substrate.

The proportion of the liquids in the mixture that is ejected must bemaintained constant and must be closely controlled. Accordingly, it isnecessary carefully to regulate the quantity of each of the liquids thatis pumped to the mixing chamber; and for this purpose, proportioningpumps of the reciprocating piston type are often used, the valves ofwhich pumps are arranged to create pumping action when stroked in eitherdirection, thus providing continuous flow. Because the pumps arebifunctionally used as a measuring device,

it is necessary to prevent cavitation; therefore the pumps mustthemselves be pressure fed.

The feeding of the proportioning pumps under pressure, however, givesrise to a problem: During the refill stroke of the proportioning pump,the feed pressure to the pump will add to the outlet pressure of thepump; while during the displacement stroke of the proportioning pump,the feed pressure becomes nullified by the closing of the inlet valve.There is thus a fluctuating variation in the outlet pressure of theproportioning pump, which in magnitude, by virtue of the mechanicaldesign of the pump, actually is multiplied to twice the feed pressure tothe proportioning pump.

Accordingly, it is an object of the .present invention to provide suchapparatus in which the outlet pressure of the proportioning pumps tendsto be much more uniform than heretofore.

Another object of the present invention is the provision of suchapparatus which will be relatively simple and inexpensive to construct,easy to operate, maintain and repair, and rugged and durable in use.

Briefly, the objects of the present invention are achieved by couplingthe two proportioning pumps in opposed tandem relationship and drivingthem by a single double-acting fluid motor. Quite unexpectedly, it hasbeen found that the undesirable pressure fluctuation at the outlet atboth proportioning pumps is thus greatly reduced and under certaincircumstances virtually eliminated.

Other objects, features and advantages of the present invention willbecome apparent from a consideration of the following description, takenin connection with the accompanying drawing, which is a schematic viewof apparatus according to the present invention.

Referring now to the drawing in greater detail, there is shown apparatusaccording to the present invention for ejecting a mixture of liquids,comprising an ejection head 1 in the form of a barrel 3 with anelongated cylindrical mixing chamber 5 therein that is open at itsdischarge end, that is, at its right hand end as seen in the drawing. Apair of opposed inlets 7 and 9 extend through the side walls of barrel 3and open into chamber 5 substantially tangentially of chamber 5. Aplunger 11 is slidably disposed in barrel 3 and is manually actuable toreciprocate between the position shown in the drawing, in which theinlet openings 7 and 9 are both exposed for the flow of materials to bemixed into chamber 5, and a rightward position as seen in the drawing inwhich plunger 11 closes the inlet openings 7 and 9 fully fills thechamber 5 thereby completely to eject the reactive mixture from chamber5. The construction and operation of ejection head 1 is known in the artand need not be further described. It can for example be as disclosed inthe above-mentioned Gusmer US. Pat. No. 3,263,928, in which case thechamber 5 is of uniform cross sectional configuration substantiallythroughout its length, including the discharge opening, so that foam maybe ejected from ejection head 1; or ejection head 1 can have the formshown in the above Gusmer US. Pat. No. 2,890,836, with a dischargeopening reduced in diameter as compared to the mixing chamber, for theejection of a spray.

The mutually reactive liquids reach ejection head 1 along separatepaths, as mentioned above. Thus, in the case of a polyurethane resin andthe activator therefor, for example, as described in the above GusmerUS. Pat. No. 3,263,928, the activator may come from a supply container13 maintained under a positive pressure of, say, 2 or 3 p.s.i.g., by asource of nitrogen 15 which prevents the entry of air and water vaporinto container 13. Activator flows from container 13 through a checkvalve 17 and then through a piston pump 19 by which its pressure iselevated for the purpose described above, for example to p.s.i.g. Frompump 19, the activator proceeds through a check valve 21 to the primarypump chamber of the activator proportioning pump 23 in which a piston 25is reciprocable under the impetus of a displacement piston rod 27.Piston 25 divides the double acting pump 23 into two chambers,

,primary chamber 29 and displacement chamber 31.

From chamber 29, activator flows through conduit 33 and check valve 35toward conduit 37 which communicates with activator inlet opening 7, andalso toward conduit 39 which communicates with chamber 31 of pump 23. Itis during the rightward stroke of piston 25, as seen in the drawing,that the pressure imparted to the activator by pump 19 tends to beadditive and the outlet pressure of pump 23 to be relatively high; whileit is during the leftward stroke of the piston 25 as seen in the drawingthat the pressure imparted by pump '19 becomes nullified and the outletpressure of pump 23 I is proportionally lower. lt is this periodicalfluctuation of the pump outlet pressure that the present inventionlargely overcomes.

On the resin side, the path of the liquid is similar, from a container39 maintained under positive pressure by nitrogen 41, through a checkvalve 43, to higher pressure through a pump 45, then through a checkvalve 47 to pump 49 including a piston 51 that divides pump 49 intochambers 53 and 55. From chamber 53, resin flows through conduit 57through a check valve 59 and thence to resin inlet conduit 61communicating with resin inlet opening 9, and also to conduit 63communicating with chamber 55.

However, piston 51 is on the same piston rod 27 as piston 25 and isaxially aligned therewith, the piston rod also being the piston rod of adouble-acting fluid motor 65 comprising a double-acting piston 67 thatdivides motor 65 into chambers 69 and 71. In the illustrated embodiment,fluid motor 65 is a hydraulic motor fed from a source of hydraulicliquid in a sump 73 through a constant pressure, variable volume pump 75and thence through an automatically periodically reversing spool valve77 actuated by a solenoid S, to conduits 79 and 81 that are alternatelyfeed and return conduits, the hydraulic liquid returning to sump 73through a return conduit 83. Alternatively, motor 65 could be an airmotor or an electric motor, so long as it remains a constant pressuremotor.

in operation, the nature of the liquids, their flow rates andtemperatures and the pressures imparted thereto by pumps 19, 29, 45 and53, may all be conventional, for example as disclosed in theabove-identified Gusmer patents, and hence need not be furthermentioned. The activator and the resin proceed from their respectivecontainers l3 and 29 through their respective pumps 19 and 45, in whichthey are elevated in pressure; although it will be understood that pumps19 and 45 can be eliminated and if the nitrogen or other dry inert gasat and 41 is of sufficiently high pressure. in any event, the liquidstreams at elevated pressure flow along parallel paths to the respectivepumps 23 and 49, the activator entering chamber 29 while the resinenters chamber 53. Piston is moving to the left relative to chamber 29at the same time that piston 51 is moving to the left relative tochamber 53, as seen in the drawing, so that the pumps 23 and 49 areacting in opposition to each other. During this particular stroke of thepumps, the valve 77 is in the position shown in the drawing, withhydraulic fluid being fed by pump 75 to chamber 71 and discharged fromchamber 69. At the end of the stroke of the piston rod 77 with itsassociated pistons 25, 51 and 67, solenoid S reverses the position ofvalve 77 so that hydraulic fluid under pressure is fed to chamber 69 andexhausted from chamber 71, whereupon piston 67 and with it the rod 27and pistons 25 and 51 is driven to the right as seen in the drawing,which reverses the stroke of both pumps 23 and 49.

As a result of the pistons 25 and 51 being thus coupled in opposedtandem relationship and actuated by the same reciprocating fluid motor,it is found that the discharge pressure in conduits 37 and 61, which inthe past might have varied from, say, about 700 to about 900 p.s.i.depending upon the direction of stroke of the pumps 23 and 49, nowvaries very little from a means pressure of 800 p.s.i.

From a consideration of the foregoing disclosure, therefore, it will beevident that all of the initially recited objects of the presentinvention have been achieved.

Although the present invention has been described and illustrated inconnection with a preferred embodiment, it is to be understood thatmodifications and variations may be resorted to without departing fromthe spirit of this invention, as those skilled in this art will readilyunderstand. Such modifications and variations are considered to bewithin the purview and scope of the present invention as defined by theappended claims.

What is claimed is:

1. Apparatus for ejecting a mixture of liquids, comprising an ejectionhead, means for separately feeding two streams of liquids from separatesources of said liquids to said ejection head and for mixing saidstreams of liquids in said ejection head, said feed means comprising apair of double-acting reciprocating piston pumps one individual to eachof said streams, means for supplying each of said pumps with liquidunder elevated pressure from a respective one of said sources, means forseparately delivering said liquids from said pumps to said ejectionhead, and means for driving said pumps in opposed tandem relationshipcomprising a double-acting reciprocating constant pressure motor commonto said pistons of said pumps.

2. Apparatus as claimed in claim 1, said motor being a fluid motorcomprising piston means and piston rod means connected to said pistonsof said pumps.

3. Apparatus as claimed in claim 2, said fluid motor being a hydraulicmotor, and means for alternately supplying hydraulic liquid to andexhausting hydraulic liquid from opposite sides of said hydraulic motor.

4. Apparatus as claimed in claim 1, said motor and said pumps being inaxially aligned relationship.

5. Apparatus as claimed in claim 1, said means for supplying liquids tosaid pumps under elevated pressure comprising positive displacementtransfer pumps one individual to each said stream.

1. Apparatus for ejecting a mixture Of liquids, comprising an ejectionhead, means for separately feeding two streams of liquids from separatesources of said liquids to said ejection head and for mixing saidstreams of liquids in said ejection head, said feed means comprising apair of double-acting reciprocating piston pumps one individual to eachof said streams, means for supplying each of said pumps with liquidunder elevated pressure from a respective one of said sources, means forseparately delivering said liquids from said pumps to said ejectionhead, and means for driving said pumps in opposed tandem relationshipcomprising a double-acting reciprocating constant pressure motor commonto said pistons of said pumps.
 2. Apparatus as claimed in claim 1, saidmotor being a fluid motor comprising piston means and piston rod meansconnected to said pistons of said pumps.
 3. Apparatus as claimed inclaim 2, said fluid motor being a hydraulic motor, and means foralternately supplying hydraulic liquid to and exhausting hydraulicliquid from opposite sides of said hydraulic motor.
 4. Apparatus asclaimed in claim 1, said motor and said pumps being in axially alignedrelationship.
 5. Apparatus as claimed in claim 1, said means forsupplying liquids to said pumps under elevated pressure comprisingpositive displacement transfer pumps one individual to each said stream.